The day before preparing the tart, place the potatoes in a saucepan and cover them with water. Place on medium heat and bring to a boil. Boil the potatoes for 10 minutes, then cover the pan, remove it from the heat and let the potatoes continue cooking until they have cooled. Remove the potatoes from the water, let them drain for a few minutes, then keep them at a cool room temperature until the next day – this helps to evaporate some excess moisture the potatoes have absorbed.

To finish the potatoes, peel and trim any blemished and grated them on the largest holes of a box grater.

Melt the butter in a saute pan on medium heat and cook the onions slowly until softened, about 15 minutes.

When you’re ready to bake the quiche, set a rack in the lowest level of the oven and preheat to 400 degrees.

Arrange the grated potatoes in the tart crust without pressing them down and scatter the cooked onion and thyme or parsley over them. Toss the cheese and flour together and scatter on the potatoes. Whisk the eggs in a bowl, season lightly with salt, pepper, and nutmeg, and whisk in the half and half.

Place the pan on the stove and pour on the custard mixture only filling to within 1/4 inch of the top of the crust.

Set the pan in the oven and immediately lower the temperature to 375 degrees. Bake until the crust is baked through and the filling is set and puffed, about 35 to 40 minutes.

Cool briefly on a rack, then unmold and serve either hot or warm.

Flaky Buttery Dough

To maximize flakiness and as much delicate buttery flavor as possible you need to use enough butter in a dough. If you remember to chill this dough after mixing and again after rolling, you’ll enjoy both a superior texture and flavor. To keep from melting the butter and creating an excessively soft dough, this is best mixed in the food processor.

Combine the flour, salt, and baking powder in the bowl of a food processor; pulse several times at 1-second intervals to mix.

Add the butter cubes and pulse again 3 or 4 times. Use a metal spatula to scrape the side of the bowl and mix butter pieces throughout the flour.

Repeat step 2.

Use a fork to beat the eggs to break them up and add them to the bowl. Pulse again until the dough almost forms a ball; avoid pulsing too much or the pieces of butter needed to make the dough flaky will become too small.

Invert the dough to a lightly floured work surface, carefully remove the blade, and quickly press it together.

Divide the dough into 2 pieces, form them into thick disks, and wrap in plastic. Chill the dough for a couple of hours before rolling.

Roll one of the disks of dough and line a 10-inch tart pan for the tart above.